Apollo vet Sy Liebergot shows Ars how NASA got men safely to the Moon and back.

HOUSTON, TEXAS—Astronauts have been saying "Houston" into their radios since 1965. The callsign refers in general to the Johnson Space Center in Texas, and the people who answer to it sit in the Mission Control Center, located in Building 30 near the south end of the The Lyndon B. Johnson Space Center (JSC) campus. "Mission Control" has been the subject of movies, television shows, and documentaries for decades. It's usually depicted as a bustling room filled with serious folks in short-sleeved white shirts and skinny black ties who shout dramatically about damaged spaceships while frantically pressing buttons on chunky 1960s control consoles. What is it really like, though, to sit at one of those consoles? What do all of those buttons do?

On a sunny morning in early October, I hopped in my car to find out. The Johnson Space Center is about a dozen miles from my home in League City, up the newly constructed NASA Bypass and down the historic NASA Road 1. After a short drive, my photographer and I were in line at JSC's main gate. We were meeting contacts from NASA's Public Affairs Office, and they were going to escort us further on-site to Building 30 for an Ars "Mission Control" tour. Our mission? Explain the technical details behind how the room operated—and what it was like to sit at a console and answer those calls from space.

Enlarge/ The exterior of Building 30, which houses the rooms collectively known as "mission control." The flag on the roof flies whenever there is at least one American in space.

One small step

This wasn't my first time in Building 30. I visited JSC with some frequency during my time at Boeing, though not often enough for the feeling of wonder to wear off. Some people are awed when they go to St. Paul's Basilica, others by visiting Disney World. To me, neither place holds a candle to the Johnson Space Center—this is the place where, 50 years ago, men and women helped execute the greatest engineering achievement in all of human history.

The original plan for my visit was simply to tour the one restored Apollo-era mission control room, to take plenty of pictures, and to give Ars readers a good technical understanding of how "Mission Control" worked during the Apollo era. NASA, however, upped the ante when it assigned my tour guide—none other than Sy Liebergot.

Enlarge/ Sy Liebergot, Apollo EECOM, with his old desk in the background.

NASA loves its acronyms

NASA's government and military roots ensure that its jargon is peppered with acronyms. In addition to being part of the culture, shortening complex concepts and names down to bite-sized phrases helps with quick and concise communication (engineers are all about efficiency). Here's a list of the acronyms used in this article:

FCR - Flight Control Room, the Shuttle-era designation for the "mission control" rooms

JSC - The Lyndon B. Johnson Space Center, in Houston, originally known as the "Manned Spaceflight Center" from 1963 to 1973. Headquarters of the manned space flight program and home of "mission control"

MCC - Mission Control Center, the section of Building 30 housing the actual "mission control" rooms

MOCR - Mission Operations Control Room, the original designation for the "mission control" rooms

MSFN - Manned Space Flight Network, a globe-spanning collection of ships and ground stations which were used to send and receive messages to and from NASA spacecraft

PABX - Private Automatic Branch Exchange, a type of local phone system which tied the JSC campus together

RTCC - Real Time Computing Complex, the room where the five mainframes which powered Mission Control were kept, along with all the necessary peripheral equipment to run them

SSR - Staff Support Room, the "back rooms" which augmented each flight controller's station

SMEK - Summary Message Keyboard, a flight control panel module which allowed a controller to call up systems data for review

The name should be familiar if you're a fan of manned space flight. Seymour Liebergot, a retired NASA Flight Controller, sat at the EECOM console for Apollo 8, 9, 10, 11, 12, 13, 14, and 15. He was one of the flight controllers responsible for ensuring the safe return of Apollo 13 following the explosion of one of its liquid oxygen tanks (in the film Apollo 13, he's played by director Ron Howard's brother, Clint). Liebergot was present for some of the most monumental moments in space flight, and he was going to walk me through the technical details of Mission Operations Control Room 2. It was like requesting a tour of the Bat Cave and having Alfred show you around the place personally.

JSC looks a lot like a college campus. Situated on 1,600 acres of wetlands between Houston and Galveston, it was constructed during 1962 and 1963, eventually becoming operational in time to shepherd Project Gemini into space. One hundred buildings sit scattered across the property, with the main cluster along NASA Road 1, interspersed with parking lots and neatly maintained green spaces. With the exception of a few recent additions, the buildings of JSC appear every bit the product of their era: 1960s modernist, most mixing terraced concrete and glass. The corridors look like they should exude the odor of decades of cigarette smoke, but the federal government's "no smoking" policy has been in place long enough that most smell faintly of stale coffee instead.

Building 30, which was recently named the "Christopher C. Kraft Jr. Mission Control Center," is a tall and mostly windowless structure, three stories in two wings, joined by a central lobby. Building 30 houses several different "mission control" rooms, which are officially called Flight Control Rooms (FCRs, pronounced "fickers"). When the building was first made operational in 1965 there were a pair of control rooms, then called Mission Operation Control Rooms (MOCRs, "mo-kers").

The MOCRs served NASA through the Shuttle era. The room that housed MOCR 1 has been remodeled and repurposed several times; it is currently used as the International Space Station FCR. MOCR 2, which was used for almost every Gemini and Apollo flight, was restored to its 1960s-era appearance after retirement in 1992. It is now a registered historic landmark.

Enlarge/ Security doors leading to Building 30's Mission Operations Wing.

MOCR 2 is on the third floor of Building 30's Mission Operations Wing. The other floors house the Shuttle and station FCRs, as well as FCR support rooms (called MPSRs, for Multi-Purpose Staff Rooms) and office space. The first floor used to house the Real Time Computing Complex, or RTCC, which during Apollo consisted of five IBM System/360 mainframes and their support equipment. As we'll see, the RTCC was a vitally important part of the MOCR's operations.

Enlarge/ A portion of the Real Time Computing Complex on the first floor of Building 30. Today, this is all regular office space.

After passing through the security doors, Liebergot and I rode an elevator up to the third floor. We walked through high-ceilinged corridors with raised floors covered in rubberized tiles, an arrangement which would be familiar to many IT workers. MOCR 2 occupies the central area of the floor, around some corners and past a low alcove containing lockers and a coffee machine. To enter, we walked up a side ramp much like you would find in a movie theater with stadium seating. MOCR 2 is indeed about the size of a small theater—in fact, the room is sometimes used by NASA to screen Apollo 13 and other space films for selected audiences.

The iconic Ford-Philco-designed consoles are arranged in four tiers stepping down from the rear of the room, separated by a glass wall from the visitor's gallery and a pair of press booths. The room is dimly lit by recessed fluorescents, and Sy informed me the room was kept even darker. That way, it's easier to see the console displays.

Enlarge/ MOCR 2, from the top row next to the DoD console, looking across at the left front rear projection screens.

Once our NASA contact cleared out some picture takers and shut the doors, MOCR 2 was suddenly cloaked in silence. I could feel the ghosts. Here, in this very room, sitting at these sage-colored consoles, 30 years of manned space flight happened. It felt very much like standing in a cathedral—except that this room wasn't just built to talk to the heavens, but to actually visit them.

Lee Hutchinson
Lee is the Senior Technology Editor at Ars and oversees gadget, automotive, IT, and culture content. He also knows stuff about enterprise storage, security, and manned space flight. Lee is based in Houston, TX. Emaillee.hutchinson@arstechnica.com//Twitter@Lee_Ars

Cathedral isn't an unreasonable comparison. If you were a child then, it could have been the most important thing you ever watched adults do. It was a welcome respite from things like riots, civil rights protests, the Viet Nam war, and price controls. The picture of the blue Earth rising over the grey horizon of the Moon might be the most significant photo ever taken. I'd probably burst into tears if I ever entered the MOCR.

Kennedy's speech at the Rice football stadium declares the Moon Shot in an almost cavalier manner. I don't think we're "unlikely to ever go again". If something crops up out there and we have to check it out, I'm sure new Sy Leibergots will be ready to help make it happen.

Look at the pic of the Super EECOM. Jersey Shore contestants and tone bending starlets would pass him by with a frown at most. But that pic will be seen in a hundred years and no one will know who the other people are.

As a big time Apollo project and manned spaceflight junkie, I loved this article. Accurate and great depth. Seymour, if you're reading...thank you..for the interview and your time in the program. Well done Lee, keep it up Ars.

Oh my gawd, you have no idea how many hours I've spent trying to glean all this info from around the web - and here it is in one perfect article. Brilliant! Thank you, thank you, thank you!

I'm intrigued by the use of the voice loop system. It's such a simple but powerful method of group communication. Is there any one that still uses always-on voice channels that you can selectively monitor or transmit on in their jobs? It seems like it would be a simple thing to do with telephony, but I've never seen software for it. Instead, we have to muck about with conference bridges and station-to-station calls.

I'm intrigued by the use of the voice loop system. It's such a simple but powerful method of group communication. Is there any one that still uses always-on voice channels that you can selectively monitor or transmit on in their jobs? It seems like it would be a simple thing to do with telephony, but I've never seen software for it. Instead, we have to muck about with conference bridges and station-to-station calls.

NASA still uses something similar today in the FCRs and the MER at JSC (and from other centers, too, from pictures I've seen). Today it's all digital, though. There are panels at every station called DVIS panels, for Digital Voice Intercommunications Subsystem, pronounced like "divas". Some more info here. I have some pics, too, from when I was last in the MER in 2007--front view, with DVIS at the edge of each desk, and back view, with signs reminding everyone to use their audio loops instead of yelling.

Great read, thanks! Crazy to think they managed to monitor so much information with such rudimentary systems compared to today... That stuff about the display of number & overlays... makes it all the more impressive!

I always wondered how they created the seemingly ahead of their time display readouts, and now I know!

In researching the technology, that was the part that shocked me the most. Everything else was reasonable--big mainframes, no software controlled panels, all hard wiring, that kind of thing. But the display stuff threw me. I had to read and re-read that section of PHO-FAM001 over and over again to make sure I was understanding it right, and even after that I sought out some corroborative info. Sy's descriptions clinched it. It really was that crazy--slides and CRTs, filmed by a video camera. Totally wild.

Fantastic article - really gave the impression of coming with you on this awesome tour of the facilities and the technical background is fascinating.

Another dramatisation, but I recommend if you have not see it look at "The Dish" about the role of a radio telescope in relaying some of the Apollo 11 pictures and telemetry back to earth. Shows the importance of the era and the human side of people involved. The DVD is good with lots of archive footage of the mission: http://www.imdb.com/title/tt0205873/

Thank you for an utterly engrossing and fascinating article. Every time I think that the achievements of the people and machines of the Space Program can't get any more impressive, I read something like this that just amazes me. What was accomplished with such rudimentary and archaic (to our current eyes) is just flat-out astonishing.

The descriptions of the display technology and the pneumatic tube system for delivering hard copies struck me as an insanely wild steam punk system. I half-expected to find that the Flight Director was seated at a massive pipe organ, orchestrating the mission!

Fantastic article and photos. Thank you for writing such a wonderful and informative piece of work.

Sometimes I think about the moon landing and the technology they used to do it, and it just blows my mind. If they attempted it today, it would still be a wildly risky operation. It was, I think, the greatest adventure ever undertaken. The only thing that comes close in my mind is Magellan's voyage around the world. Just an utter leap into the dark.

Lee, thank you for the fantastic article! It's amazing what those guys achieved with the tools they had. My father worked on the Surveyor probes, and loved to tell stories from that time. I wish he were still around, because I'd love to hear those stories again.

Thank you so much for this wonderful article. Watching the moon landing on a black & white tv before I was two is probably my earliest memory, and set me on course for a life in science and engineering. Thank you Sy and the other controllers, you changed so many lives.

Oh my gawd, you have no idea how many hours I've spent trying to glean all this info from around the web - and here it is in one perfect article. Brilliant! Thank you, thank you, thank you!

I'm intrigued by the use of the voice loop system. It's such a simple but powerful method of group communication. Is there any one that still uses always-on voice channels that you can selectively monitor or transmit on in their jobs? It seems like it would be a simple thing to do with telephony, but I've never seen software for it. Instead, we have to muck about with conference bridges and station-to-station calls.

Air traffic controllers use a similar system where they can monitor, talk, and override multiple channels to coordinate with other controllers.

Last time I was at the MCC, they had us sit in those chairs and then they played the Apollo 1 recording from that fatal accident. I don't know if that's a regular feature of the tour (or if your guide did the same for you), but it really impressed on me the gravity of human spaceflight. No pun intended.